The 67gallium-transferrin pulmonary leak index in patients at risk for the acute respiratory distress syndrome

Serial inflammatory biomarkers of the severity, course and outcome of late onset acute respiratory distress syndrome in critically ill patients with or at risk for the syndrome after new-onset fever

AIM

Accurate biomarkers of the acute respiratory distress syndrome (ARDS) may help risk stratification and management. We assessed the relation between several biomarkers and the severity, course and outcome of late onset ARDS in 101 consecutive critically ill patients with new onset fever.

MATERIALS AND METHODS

On study days 0, 1, 2 and 7 we measured angiopoietin-2 (ANG2), pentraxin-3 (PTX3), interleukin-6 (IL-6), procalcitonin (PCT) and midregional proadrenomedullin (proADM). ARDS was defined by the Berlin definition and by the lung injury score (LIS).

RESULTS

At baseline, 48% had ARDS according to the Berlin definition and 86% according to the LIS. Baseline markers poorly predicted maximum Berlin categories attained within 7 days, whereas ANG2 best predicted maximum LIS. Depending on the ARDS definition, the day-by-day area under the receiver operating characteristic curves suggested greatest monitoring value for IL-6 and PCT, followed by ANG2. ANG2 and proADM predicted outcome, independently of disease severity.

CONCLUSION

Whereas IL-6 and PCT had some disease monitoring value, ANG2 was the only biomarker capable of both predicting the severity, monitoring the course and predicting the outcome of late onset ARDS in febrile critically ill patients, irrespective of underlying risk factor, thereby yielding the most specific ARDS biomarker among those studied.

Albumin rather than C-reactive protein may be valuable in predicting and monitoring the severity and course of acute respiratory distress syndrome in critically ill patients with or at risk for the syndrome after new onset fever

BACKGROUND

We studied the value of routine biochemical variables albumin, C-reactive protein (CRP) and lactate dehydrogenase (LDH) to improve prediction and monitoring of acute respiratory distress syndrome (ARDS) severity in the intensive care unit.

METHODS

In 101 critically ill patients, with or at risk for ARDS after new onset fever, data were collected on days (D) 0, 1, 2, and 7 after inclusion. ARDS was defined by the Berlin definition and lung injury score (LIS).

RESULTS

At baseline, 48 patients had mild to severe ARDS according to Berlin and 87 according to LIS (Rs = 0.54, P < 0.001). Low baseline albumin levels were moderately associated with maximum Berlin and LIS categories within 7 days; an elevated CRP level was moderately associated with maximum Berlin categories only. The day-by-day Berlin and LIS categories were inversely associated with albumin levels (P = 0.01, P < 0.001) and directly with CRP levels (P = 0.02, P = 0.04, respectively). Low albumin levels had monitoring value for ARDS severity on all study days (area under the receiver operating characteristic curve, AUROC, 0.62-0.82, P < 0.001-0.03), whereas supranormal CRP levels performed less . When the Berlin or LIS category increased, albumin levels decreased ≥1 g/L (AUROC 0.72-0.77, P = 0.001) and CRP increased ≥104 mg/L (only significant for Berlin, AUROC 0.69, P = 0.04). When the LIS decreased, albumin levels increased ≥1 g/L (AUROC 0.68, P = 0.02). LDH was higher in 28-day non-survivors than survivors (P = 0.007).

CONCLUSIONS

Overall, albumin may be of greater value than CRP in predicting and monitoring the severity and course of ARDS in critically patients with or at risk for the syndrome after new onset fever. Albumin levels below 20 g/L as well as a decline over a week are associated with ARDS of increasing severity, irrespective of its definition. LDH levels predicted 28-day mortality.

Soluble receptor for advanced glycation end products as an indicator of pulmonary vascular injury after cardiac surgery

Background

Cardiac surgery is frequently complicated by an acute vascular lung injury and this may be mediated, at least in part, by the (soluble) receptor for advanced glycation end products (sRAGE).

Methods

In two university hospital intensive care units, circulating sRAGE was measured together with the ⁶⁸Gallium-transferrin pulmonary leak index (PLI), a measure of pulmonary vascular permeabiliy, in 60 consecutive cardiac surgery patients stratified by the amount of blood transfusion, within 3 hours of admission to the intensive care.

Results

Cardiac surgery resulted in elevated plasma sRAGE levels compared to baseline (315 ± 181 vs 110 ± 55 pg/ml, P = 0.001). In 37 patients the PLI was elevated 50% above normal. The PLI correlated with sRAGE (r² = 0.11, P = 0.018). Plasma sRAGE discriminated well between those with an elevated PLI and those with a normal PLI (area under the operator curve 0.75; P = 0.035; 95% CI 0.55-0.95), with 91% sensitivity but low specificity of 36% at a cutoff value of 200 pg/mL. Blood transfusion did not influence sRAGE levels.

Conclusions

sRAGE is elevated in plasma after cardiac surgery and indicates increased pulmonary vascular permeability. The level of sRAGE is not affected by transfusion.

Pre-treatment with allopurinol or uricase attenuates barrier dysfunction but not inflammation during murine ventilator-induced lung injury

Introduction

Uric acid released from injured tissue is considered a major endogenous danger signal and local instillation of uric acid crystals induces acute lung inflammation via activation of the NLRP3 inflammasome. Ventilator-induced lung injury (VILI) is mediated by the NLRP3 inflammasome and increased uric acid levels in lung lavage fluid are reported. We studied levels in human lung injury and the contribution of uric acid in experimental VILI.

Methods

Uric acid levels in lung lavage fluid of patients with acute lung injury (ALI) were determined. In a different cohort of cardiac surgery patients, uric acid levels were correlated with pulmonary leakage index. In a mouse model of VILI the effect of allopurinol (inhibits uric acid synthesis) and uricase (degrades uric acid) pre-treatment on neutrophil influx, up-regulation of adhesion molecules, pulmonary and systemic cytokine levels, lung pathology, and regulation of receptors involved in the recognition of uric acid was studied. In addition, total protein and immunoglobulin M in lung lavage fluid and pulmonary wet/dry ratios were measured as markers of alveolar barrier dysfunction.

Results

Uric acid levels increased in ALI patients. In cardiac surgery patients, elevated levels correlated significantly with the pulmonary leakage index. Allopurinol or uricase treatment did not reduce ventilator-induced inflammation, IκB-α degradation, or up-regulation of NLRP3, Toll-like receptor 2, and Toll-like receptor 4 gene expression in mice. Alveolar barrier dysfunction was attenuated which was most pronounced in mice pre-treated with allopurinol: both treatment strategies reduced wet/dry ratio, allopurinol also lowered total protein and immunoglobulin M levels.

Conclusions

Local uric acid levels increase in patients with ALI. In mice, allopurinol and uricase attenuate ventilator-induced alveolar barrier dysfunction.

The effect of blood transfusion on pulmonary permeability in cardiac surgery patients: a prospective multicenter cohort study

BACKGROUND

There is an association between blood transfusion and pulmonary complications in cardiac surgery. Mediators of increased pulmonary vascular leakage after transfusion are unknown. We hypothesized that factors may include antibodies or bioactive lipids, which have been implicated in transfusion-related acute lung injury.

STUDY DESIGN AND METHODS

We performed a prospective cohort study in two university hospital intensive care units in the Netherlands. Pulmonary vascular permeability was measured in cardiac surgery patients after receiving no, restrictive (one or two transfusions), or multiple (five or more transfusions) transfusions (n=20 per group). The pulmonary leak index (PLI), using (67) Ga-labeled transferrin, was determined within 3 hours postoperatively. Blood products were screened for bioactive lipid accumulation and the presence of antibodies.

RESULTS

The PLI was elevated in all groups after cardiac surgery. Transfused patients had a higher PLI compared to nontransfused patients (33×10(-3) ± 20×10(-3) vs. 23×10(-3) ± 11×10(-3)/min, p<0.01). The amount of red blood cell (RBC) products, but not of fresh-frozen plasma or platelets, was associated with an increase in PLI (β, 1.6 [0.2-3.0]). Concerning causative factors in the blood product, neither the level of bioactive lipids nor the presence of antibodies was associated with an increase in PLI. Patient factors such as surgery risk and time on cardiopulmonary bypass did not influence the risk of pulmonary leakage after blood transfusion.

CONCLUSIONS

Transfusion in cardiothoracic surgery patients is associated with an increase in pulmonary capillary permeability, an effect that was dose dependent for RBC products. The level of bioactive lipids or the presence of HLA or HNA antibodies in the transfused products were not associated with increased pulmonary capillary permeability.

Plasma protein levels are markers of pulmonary vascular permeability and degree of lung injury in critically ill patients with or at risk for acute lung injury/acute respiratory distress syndrome

OBJECTIVES

To evaluate the diagnostic value of plasma protein levels for pulmonary vascular permeability and acute respiratory distress syndrome. During acute lung injury and acute respiratory distress syndrome, increased vascular permeability induces protein-rich fluid extravasation. We hypothesized that plasma protein levels predict increased vascular permeability and acute respiratory distress syndrome.

DESIGN

A prospective, observational study.

PATIENTS

Eighty-three consecutive, mechanically ventilated patients with or at risk for acute lung injury/acute respiratory distress syndrome, of whom 18 had sepsis. Patients with increased pulmonary capillary wedge pressures or central venous pressures were excluded.

INTERVENTIONS

Patients were subjected to pulmonary capillary wedge pressure/central venous pressure-guided fluid loading with saline or colloid fluids.

MEASUREMENTS AND MAIN RESULTS

We measured plasma albumin and transferrin levels and determined the Gallium-transferrin pulmonary leak index, the American European Consensus Conference criteria, and the lung injury score. Measurements were performed before and after fluid loading to evaluate effects of fluid loading. Plasma albumin and transferrin levels were approximately 30% lower in acute respiratory distress syndrome than patients with acute lung injury (p < .01) and patients without lung injury (p < .05). Protein levels inversely related to the pulmonary leak index (standardized regression coefficient -0.28, p < .001 for albumin; standardized regression coefficient -0.30, p = .003 for transferrin) and the lung injury score (standardized regression coefficient -0.19, p = .01 for albumin), independently of presence of sepsis, severity of disease, and fluid loading. Albumin and transferrin levels had a high sensitivity (77-93%) and negative predictive value (80-98%) for elevated pulmonary vascular permeability and acute respiratory distress syndrome (American European Consensus Conference criteria and lung injury score). The addition of hypoalbuminemia (<17.5 g/L) and hypotransferrinemia (<0.98 g/L) as criteria to the American European Consensus Conference criteria or the lung injury score increased their predictive values for elevated pulmonary vascular permeability.

CONCLUSIONS

In critically ill patients, decreased plasma albumin and transferrin levels parallel increased pulmonary vascular permeability irrespective of underlying disease and fluid status. While normal levels help to exclude acute respiratory distress syndrome, hypoalbuminemia and hypotransferrinemia increase the diagnostic accuracy of the American European Consensus Conference criteria and lung injury score for elevated pulmonary vascular permeability.

Update on transfusion solutions during surgery: review of hydroxyethyl starches 130/0.4

OBJECTIVES

Restoration of circulation is crucial in the surgical patient management. Colloids and crystalloids are widely used for blood volume therapy. We reviewed recent trials to evaluate efficacy and safety of hydroxyethyl starch (HES) 130/0.4 during surgery.

MATERIAL AND METHODS

A subjective, not systematic, review of literature was performed. Papers were searched to answer questions about efficacy of HES, its impact on coagulation and inflammation and its effects on pulmonary mechanics and renal function.

CONCLUSIONS

HES 130/0.4 is effective for volume therapy and is less expensive than human albumin. Its effects on coagulation and renal function are manageable; it may ameliorate pulmonary permeability and reduce inflammation.

The current state in the evaluation and treatment of ARdS and SIRS

Trauma, the number one cause of death until the fourth decade of life, causes an inflammatory response. This response in its extreme is associated with the development of the systemic inflammatory state, adult respiratory distress syndrome, multi-organ failure, and death. The inflammatory response is mediated via multiple pathways- the inflammatory-cytokine, immunologic, coagulation and endocrine pathways. It is countered by producing antiinflammatory mediators. This reaction is altered in elderly patients. Knowledge of the patient's prior medical problems and the differential diagnosis for the possible causes of the current condition should help direct the surgical intervention and supportive care in an attempt to stabilize the patient. With the improvement of monitoring and diagnostic technologies, understanding the significance of the inflammatory pathways in trauma patients will decrease morbidity and mortality in this group of patients.

Small animal PET for the evaluation of an animal model of genital infection

BACKGROUND

[(18)F]-FDG is a widely used tracer for the non-invasive evaluation of hypermetabolic processes like cancer and inflammation. However, [(18)F]-FDG is considered inaccurate for the diagnosis of urinary tract and genital infections because of its urinary excretion. Since the 1970s, Gallium scintigraphy is a well established test that has been used for the evaluation of inflammation and infection in human patients.

AIM

The aim of this study was to assess the feasibility of (68)Ga-Chloride small animal PET for the analysis of an animal model of genital infection, induced after the vaginal inoculum of Chlamydia muridarum. Material and Thirty mice were infected by placing 15 microl sucrose phosphate glutamic acid (SPG) 10(7) inclusion forming units of C. muridarum into the vaginal vault. As controls of inflammation, three animals were challenged with 15 microl of SPG and one healthy animal was used to assess the tracer biodistribution. Four animals died during the experiment. Eleven animals were evaluated with (68)Ga-Chloride small animal PET (GE, eXplore Vista) 3-5, 10-12, 17-19 days after infection, as well as three controls of inflammation and one healthy animal. Infection was monitored by obtaining cervical-vaginal swabs from all the animals on the day of each PET procedure. Moreover, five groups of three animals each were killed at 6, 13, 20, 27 and 34 days after infection were studied.

RESULTS

(68)Ga-PET turned out positive in all the infected animals, concordantly to data obtained by the cervical swabs and by the ex vivo analysis. The tumour-to-background ratio (TBR) decreased over time as the inflammation tended to naturally extinguish. The controls showed a slightly increased uptake of tracer due to the aseptic inflammation caused by SPG and frequent cervical swabs. The healthy control did not show any pelvic uptake.

CONCLUSION

(68)Ga-Chloride is a promising tracer for the assessment of genital infection in a mouse animal model.

Extravascular lung water to blood volume ratios as measures of permeability in sepsis-induced ALI/ARDS

OBJECTIVE

We studied the relationship, and the effect of fluid loading on this, between the ratio of extravascular lung water (EVLW) to intrathoracic/pulmonary blood volumes (ITBV, PBV) and the radionuclide pulmonary leak index (PLI) to protein during sepsis-induced acute lung injury/acute respiratory distress syndrome (ALI/ARDS).

DESIGN AND SETTING

A prospective observational study, in the intensive care unit of a university hospital.

PATIENTS

Twenty-two consecutive mechanically ventilated patients with sepsis-related ALI/ARDS from pneumonia (n = 12) or extrapulmonary sources (n = 10), without elevated cardiac filling pressures.

INTERVENTION

Crystalloid (1700-1800 ml) or colloid (1000-1800 ml) fluid loading until target filling pressures.

MEASUREMENTS AND RESULTS

Protein permeability was assessed noninvasively over the lungs with help of 67Ga-labeled transferrin and 99mTc-labeled red blood cells (Pulmonary leak index, upper limit normal 14.1 x 10(-3)/min) and EVLW and blood volumes by the thermal-dye transpulmonary dilution technique before and after fluid loading. Prior to fluids the pulmonary leak index related to the ratio of EVLW/ITBV and EVLW/PBV (r(s) = 0.46) particularly when the pulmonary leak index was below 100 x 10(-3)/min and in extrapulmonary sepsis (PLI vs. EVLW/PBV r(s) = 0.71). Fluid loading did not alter EVLW, EVLW/ITBV, or EVLW/PBV or the relationship to PLI.

CONCLUSION

The data demonstrate that EVLW/ITBV or EVLW/PBV are imperfect measures of increased protein permeability in mechanically ventilated patients with sepsis-induced ALI/ARDS particularly when the PLI is severely increased and during pneumonia, independent of fluid status.

Excess circulating angiopoietin-2 may contribute to pulmonary vascular leak in sepsis in humans

BACKGROUND

Acute respiratory distress syndrome (ARDS) is a devastating complication of numerous underlying conditions, most notably sepsis. Although pathologic vascular leak has been implicated in the pathogenesis of ARDS and sepsis-associated lung injury, the mechanisms promoting leak are incompletely understood. Angiopoietin-2 (Ang-2), a known antagonist of the endothelial Tie-2 receptor, was originally described as a naturally occurring disruptor of normal embryonic vascular development otherwise mediated by the Tie-2 agonist angiopoietin-1 (Ang-1). We hypothesized that Ang-2 contributes to endothelial barrier disruption in sepsis-associated lung injury, a condition involving the mature vasculature.

METHODS AND FINDINGS

We describe complementary human, murine, and in vitro investigations that implicate Ang-2 as a mediator of this process. We show that circulating Ang-2 is significantly elevated in humans with sepsis who have impaired oxygenation. We then show that serum from these patients disrupts endothelial architecture. This effect of sepsis serum from humans correlates with measured Ang-2, abates with clinical improvement, and is reversed by Ang-1. Next, we found that endothelial barrier disruption can be provoked by Ang-2 alone. This signal is transduced through myosin light chain phosphorylation. Last, we show that excess systemic Ang-2 provokes pulmonary leak and congestion in otherwise healthy adult mice.

CONCLUSIONS

Our results identify a critical role for Ang-2 in disrupting normal pulmonary endothelial function.

Effect of fluid loading with saline or colloids on pulmonary permeability, oedema and lung injury score after cardiac and major vascular surgery

BACKGROUND

The optimal type of fluid for treating hypovolaemia without evoking pulmonary oedema is still unclear, particularly in the presence of pulmonary vascular injury, as may occur after cardiac and major vascular surgery.

METHODS

In a single-centre, prospective, single-blinded clinical trial 67 mechanically ventilated patients were randomly assigned to receive saline, gelatin 4%, HES 6% or albumin 5%, according to a 90 min fluid loading protocol with target central venous pressure of 13 and pulmonary capillary wedge pressure of 15 mm Hg, within 3 h after cardiac or major vascular surgery. Before and after the protocol, we recorded haemodynamics and ventilatory variables and took chest radiographs. The pulmonary vascular injury was evaluated using the 67Ga-transferrin pulmonary leak index (PLI) and extravascular lung water (EVLW). Plasma colloid osmotic pressure (COP) was determined and the lung injury score (LIS) was calculated.

RESULTS

More saline was infused than colloid solutions (P<0.005). The COP increased in the colloid groups and decreased in patients receiving saline. Cardiac output increased more in the colloid groups. At baseline, PLI and EVLW were above normal in 60 and 30% of the patients, with no changes after fluid loading, except for a greater PLI decrease in HES than in gelatin-loaded patients. The oxygenation ratio improved in all groups. In the colloid groups, the LIS increased, because of a decrease in total respiratory compliance, probably associated with an increase in intrathoracic plasma volume.

CONCLUSIONS

Provided that fluid overloading is prevented, the type of fluid used for volume loading does not affect pulmonary permeability and oedema, in patients with acute lung injury after cardiac or major vascular surgery, except for HES that may ameliorate increased permeability. During fluid loading, changes in LIS (and respiratory compliance) do not represent changes in pulmonary permeability or oedema.

Usefulness of pulmonary vascular leakiness assessment in interstitial pneumonitis

STUDY OBJECTIVE

Pulmonary vascular leakiness of (67)Ga-circulating transferrin in interstitial pneumonitis (IP) was estimated by our previously described method, and its ability to evaluate disease activity was compared with conventional (67)Ga scintigraphy.

DESIGN

Using 30-min dynamic scanning data after IV injection of (67)Ga citrate, the exponential equilibration coefficient of (67)Ga between the intravascular and pulmonary interstitial compartments was calculated and defined as the leak index (LI). Pulmonary (67)Ga uptake was assessed by gallium index, determined by conventional static images taken 48 h after (67)Ga citrate injection.

SETTING

Hospitalized patients.

PARTICIPANTS

The study population consisted of 17 control patients and 20 patients with IP.

RESULTS

The mean LI in patients with IP was significantly higher than in the control group (p < 0.0001), whereas no significant increase in gallium index was noted between the IP group and the control group. No significant correlation was found between gallium index and LI among all study participants. Mean LI in patients with active IP was significantly higher than in patients with stable IP (p = 0.0024).

CONCLUSIONS

An increase in pulmonary vascular leakiness was found in patients with IP. LI may be useful to assess the disease activity.

Pulmonary endothelial permeability and circulating neutrophil-endothelial markers in patients undergoing esophagogastrectomy

OBJECTIVE

Esophagogastrectomy is an established surgical treatment for esophageal malignancy. The postoperative period may be complicated by the development of acute lung injury syndromes and thus, may provide a useful model in which to study the early pathogenic mechanisms of inflammatory lung injury.

DESIGN

Open, prospective study.

SETTING

High dependency and intensive therapy units.

PATIENTS

Eight healthy male volunteers and 20 patients in the early postoperative period

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The lung protein accumulation index (PAI) of radiolabeled transferrin was determined by using a portable, double-isotope system. The following circulating inflammatory markers-thought to reflect neutrophil-endothelial activation and injury including circulating neutrophil elastase-soluble L-, E-, and P-selectins and thrombomodulin and von Willebrand factor antigen were assayed from venous blood samples The PAI for healthy volunteers was median -0.5 (range, -1.73 to 0.27) x 10(-3)/min and for patients undergoing esophagogastrectomy -0.005 (range, -1.53 to 2.28) x 10(-3)/min. There was no statistical difference between the two groups. In the postesophagogastrectomy group, a significant elevation in circulating levels of neutrophil elastase, soluble P- and E-selectin, thrombomodulin, and von Willebrand factor antigen were observed relative to the control group but only circulating plasma elastase demonstrated a significant correlation with the PAI (r2 = .23, p =.03).

CONCLUSIONS

The data suggest patients undergoing esophagogastrectomy develop a inflammatory response but this is not a surrogate of permeability and other factors are likely to determine persistent injury to the alveolar-capillary barrier function in this patient group.